CN114275731A - MEMS-based double-beam type micro-pressure sensing core and preparation process thereof - Google Patents
MEMS-based double-beam type micro-pressure sensing core and preparation process thereof Download PDFInfo
- Publication number
- CN114275731A CN114275731A CN202111560497.9A CN202111560497A CN114275731A CN 114275731 A CN114275731 A CN 114275731A CN 202111560497 A CN202111560497 A CN 202111560497A CN 114275731 A CN114275731 A CN 114275731A
- Authority
- CN
- China
- Prior art keywords
- pressure sensing
- mems
- sensing core
- sensitive film
- etching
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Abstract
The invention discloses a MEMS-based dual-beam type micro-pressure sensing core body, which comprises a pressure sensing core body, metal bonding pads, interconnection leads, piezoresistive strips, a sensitive film, a passivation layer, an insulating layer, a back cavity and a support substrate support, wherein the rest of the pressure sensing core body except the metal bonding pad area for subsequent lead bonding is covered by the surface passivation layer, the four piezoresistive strips are connected in an open-loop Wheatstone mode through the metal bonding pads and the interconnection leads, the piezoresistive strips comprise transverse piezoresistive strips and longitudinal piezoresistive strips and are arranged in a stress concentration area of the sensitive film, and the sensitive film is suspended above the back cavity and supported by the support substrate. The invention relates to a double-beam type micro-pressure sensing core body based on an MEMS (micro-electromechanical system) and a preparation process thereof.
Description
Technical Field
The invention belongs to the technical field of micro-pressure sensing, and particularly relates to a double-beam type micro-pressure sensing core body based on an MEMS (micro-electromechanical system) and a preparation process thereof.
Background
The MEMS, i.e., Micro-Electro-Mechanical System, is referred to as MEMS process, and is based on semiconductor Micro-machining technology and ultra-precision machining technology, and the MEMS device is often in the range of μm to mm in size, and can be manufactured by most processes familiar to the integrated circuit industry. To measure ambient pressure, MEMS pressure sensors of different sensing principles have been developed, including piezoresistive (resistivity change), capacitive (capacitance change), piezoelectric (charge generation), optical, and resonant (resonant frequency change) sensing. These sensing technologies have their own advantages and disadvantages, but piezoresistive pressure sensors have become the most popular choice for various applications due to their small size, high sensitivity, low cost and simplicity of manufacture. However, the side core of the pressure bar has some problems: in the field of micro-pressure sensing, the linearity and sensitivity of the device are always key factors for restricting the large-scale application of the MEMS piezoresistive pressure sensing core body in the field. For sensing lower pressures (< 5kPa), the sensitivity must be sufficient, and if a flat membrane structure is used, the sensitive membrane must be very thin, however, a thinner membrane results in greater membrane deflection, and thus less linearity. In order to alleviate the contradiction between sensitivity and linearity, the currently adopted strategy is to etch an island structure on the back surface of the sensitive film, wherein the shape of the island can be round or square, the number of the islands can be one or two, and the size of the sensitive film is properly increased, so that the contradiction between sensitivity and linearity can be alleviated. But this increases the size of the core at the same time. The piezoresistive strips need to be placed at accurate positions on the sensitive film, the difficulty of photoetching alignment is increased due to the preparation of the island structure, the pressure and the accuracy of output signals of the sensor are greatly reduced due to slight deviation, and the yield of the MEMS sensing core body is low. In addition, the cost of increasing the size of the individual cores increases. Therefore, it is necessary to design a dual-beam type micro-pressure sensing core based on MEMS and a manufacturing process thereof.
Disclosure of Invention
The present invention is directed to solving the above problems, and provides a dual-beam type micro-pressure sensing core based on MEMS and a manufacturing process thereof, which solves the problems mentioned in the background art.
In order to solve the problems, the invention provides a double-beam type micro-pressure sensing core based on MEMS and a technical scheme of a preparation process thereof:
a dual-beam type micro-pressure sensing core based on an MEMS comprises a pressure sensing core body, metal bonding pads, interconnection leads, piezoresistive strips, a sensitive film, a passivation layer, an insulating layer, a back cavity and a supporting substrate support, wherein the rest parts of the pressure sensing core body except the metal bonding pad area for subsequent lead bonding are covered by the surface passivation layer, the four piezoresistive strips are connected in an open-loop Wheatstone mode through the metal bonding pads and the interconnection leads, the piezoresistive strips comprise transverse piezoresistive strips and longitudinal piezoresistive strips and are arranged in a stress concentration area of the sensitive film, the sensitive film is suspended above the back cavity and supported by the supporting substrate, the rest parts of the piezoresistive strips and the interconnection leads are separated by the insulating layer except contact positions, and grooves formed by etching, protruding center blocks and a dual-beam type structure are arranged on the sensitive film.
A preparation process of a double-beam type micro-pressure sensing core based on MEMS comprises the following steps:
a) corroding a V-shaped structure space on the substrate wafer by using a wet etching bulk silicon process, wherein the V-shaped structure space is used for a back cavity of the pressure sensing core body;
b) bonding a silicon wafer for preparing a sensitive film on the silicon wafer forming the back cavity by using a bonding process;
c) thinning the wafer of the sensitive film layer to a specified thickness by using a mechanical thinning process;
d) depositing a layer of silicon oxide on the surface of a bonded wafer by using a thermal oxidation process, preparing an ohmic contact region and a piezoresistive strip on a pressure sensitive film of a monocrystalline silicon wafer by using a thick boron doping process and a light boron doping process, and repairing the lattice damage caused by injection by using an annealing process after the injection is finished;
e) corroding the silicon oxide layer on the sensitive film layer by using a corrosion process, and depositing on the monocrystalline silicon pressure sensitive film by using an MEMS film deposition process to form an insulating layer with the thickness of 450 nm; forming an end point electrical contact hole of the piezoresistive strip on the insulating layer by using an etching process; depositing an Al metal film on the insulating layer by using an MEMS film deposition process, forming a metal interconnection lead by patterning and etching, and ensuring the formation of an ohmic contact region between the piezoresistive strips and the metal Al by using an annealing process;
f) after the patterning process, etching a corresponding groove with concentrated stress on the front surface of the sensitive film layer through an etching process;
g) depositing a layer of surface passivation layer on the patterned metal lead by using an MEMS film deposition process, wherein the thickness of the surface passivation layer is about 500 nm;
h) and (3) forming electrode holes for routing the PAD positions of the four graphical metal leads and the outside on the surface passivation layer by utilizing an etching process, optionally, mechanically thinning the back silicon substrate, wherein thinning and non-thinning can be selected according to the application type of preparing the pressure sensing core body, thinning is not needed if the back silicon substrate is an absolute pressure type, and the back substrate is thinned if the back silicon substrate is a differential pressure type until a back cavity can be communicated with the outside.
Preferably, the etching back cavity process in the step a) is a wet etching process.
Preferably, the bonding process in step b) is a fusion bonding process.
Preferably, in the step d), an ohmic contact region and a piezoresistive strip are prepared on the monocrystalline silicon piece pressure sensitive film by using a dense boron doping process and a dilute boron doping process, the dense boron doping process is omitted according to the process conditions, and the piezoresistive strip region is directly interconnected with the metal lead.
Preferably, the deposition process of the MEMS film in the step d) is one of a thermal oxidation process, a low pressure chemical vapor deposition process, and a plasma enhanced chemical vapor deposition process.
Preferably, the deposition process of the MEMS metal film in the step e) is one of a sputtering deposition process, an electron beam evaporation deposition process, and a heating evaporation deposition process.
Preferably, the etching process in the steps e), f) and h) is one of a dry ion etching process, a gas phase etching process, a wet anisotropic etching process and a wet isotropic etching process.
The invention has the beneficial effects that: the invention relates to a double-beam type micro-pressure sensing core based on MEMS and a preparation process thereof, which have the characteristics of convenient processing and sensitive sensing, and compared with the traditional double-beam type micro-pressure sensing core based on MEMS and the preparation process thereof, the double-beam type micro-pressure sensing core based on MEMS and the preparation process thereof have the following beneficial effects in specific use:
1. the double-beam sensitive film structure design increases the concentration degree and the uniformity of stress, and avoids the difficulty of complex preparation process of the island structure.
2. The measuring range can be as low as 2.5kPa under the conditions that the core body size is 2 multiplied by 2mm (without scribing channels) and the sensitive film thickness is 15 um.
3. The back cavity adopts a preparation process combining wet etching and fusion bonding, and compared with a common wet etching scheme, the occupancy rate of the opening area of the back cavity to the substrate supporting area is reduced, and the utilization rate of the wafer is greatly improved.
4. The pressure sensing core body of the invention completely adopts the siliceous wafer, thereby avoiding the process difficulties of difficult corrosion of vent holes and subsequent cutting caused by bonding glass substrates and the thermal stress caused by different thermal expansion coefficients of glass and silicon.
Description of the drawings:
for ease of illustration, the invention is described in detail by the following detailed description and the accompanying drawings.
FIG. 1 is a schematic perspective view of a MEMS piezoresistive pressure sensing core according to the present invention;
FIG. 2 is a front plan view of the pressure sensing core of FIG. 1 of the present invention;
FIG. 3 is a cross-sectional schematic view of the pressure sensing core of FIG. 1 of the present invention;
FIG. 4 is a schematic diagram showing a comparison of chip utilization rates of the trapezoidal back cavity and the V-shaped back cavity of FIG. 3 according to the present invention;
FIG. 5 is a schematic cross-sectional view of a pressure sensing core of the present invention;
FIG. 6 is a schematic sectional view of the preparation a of the present invention;
FIG. 7 is a schematic sectional view of the preparation b step of the present invention;
FIG. 8 is a schematic sectional view of the step of preparation c of the present invention;
FIG. 9 is a schematic sectional view of the preparation d of the present invention;
FIG. 10 is a schematic cross-sectional view of preparation e of the present invention;
FIG. 11 is a schematic sectional view of the preparation f of the present invention;
FIG. 12 is a schematic sectional view of the preparation g step of the present invention;
FIG. 13 is a schematic sectional view of the preparation h of the present invention.
In the figure: 1. a pressure sensing core; 2. a metal pad; 3. a metal lead; 4. a piezoresistive strip; 4-1, transverse piezoresistive strips; 4-2, longitudinal piezoresistive strips; 5. a center block; 6. a double beam structure; 7. a recessed region; 8. a sensitive film; 9. a surface passivation layer; 10. an insulating layer; 11. a back cavity; 12. the support substrate supports.
The specific implementation mode is as follows:
as shown in fig. 1 to 13, the following technical solutions are adopted in the present embodiment:
example (b):
a MEMS-based dual-beam type micro-pressure sensing core body comprises a pressure sensing core body 1, metal pads 2, interconnection leads 3, piezoresistive strips 4, a sensitive film 8, a passivation layer 9, an insulating layer 10, a back cavity 11 and a support substrate support 12, wherein the rest of the pressure sensing core body 1 except the metal pads 2 for subsequent lead bonding is covered by a surface passivation layer 9, the sensing core body can be prevented from being interfered by the outside during actual work, the four piezoresistive strips 4 are connected in an open-loop Wheatstone mode through the metal pads 2 and the interconnection leads 3, the piezoresistive strips 4 comprise transverse piezoresistive strips 4-1 and longitudinal piezoresistive strips 4-2 and are arranged in a stress concentration area of the sensitive film 8, the sensitive film 8 is suspended above the back cavity 11 and is supported by the support substrate support 12, and contact positions between the piezoresistive strips 4 and the interconnection leads 3 are excluded, the rest of the sensitive film is separated by an insulating layer 10, and the sensitive film is provided with a groove 7 formed by etching, a convex central block 5 and a double-beam structure 6.
A preparation process of a double-beam type micro-pressure sensing core based on MEMS comprises the following steps:
a) corroding a V-shaped structure space on the substrate wafer by using a wet method silicon corrosion process, wherein the V-shaped structure space is used for a back cavity 11 of the pressure sensing core body 1;
b) bonding a silicon wafer for preparing the sensitive film 8 on the silicon wafer forming the back cavity 11 by using a bonding process;
c) thinning the wafer of the sensitive film layer to a specified thickness by using a mechanical thinning process;
d) depositing a layer of silicon oxide on the surface of a bonded wafer by using a thermal oxidation process, preparing an ohmic contact region and a piezoresistive strip 4 on a pressure sensitive film of a monocrystalline silicon wafer by using a thick boron doping process and a light boron doping process, and repairing the lattice damage caused by injection by using an annealing process after the injection is finished;
e) corroding the silicon oxide layer on the sensitive film layer by using a corrosion process, and depositing on the monocrystalline silicon pressure sensitive film by using an MEMS film deposition process to form an insulating layer 10 with the thickness of 450 nm; and an etching process is utilized to form an end point electrical contact hole of the piezoresistive strip 4 on the insulating layer 10; depositing an Al metal film on the insulating layer 10 by using an MEMS film deposition process, forming a metal interconnection lead by patterning and then etching, and ensuring the formation of an ohmic contact region between the piezoresistive strips 4 and the metal Al by using an annealing process;
f) after the patterning process, etching a corresponding groove with concentrated stress on the front surface of the sensitive film layer through an etching process;
g) depositing a layer of surface passivation layer 9 on the patterned metal lead 3 by using an MEMS film deposition process, wherein the thickness of the surface passivation layer is about 500 nm;
h) and (3) forming electrode holes for routing with the outside at the PAD positions of the four patterned metal leads 3 on the surface passivation layer 9 by utilizing an etching process, optionally, mechanically thinning the back silicon substrate, wherein thinning and non-thinning can be selected according to the application type of preparing the pressure sensing core body 1, thinning is not needed if the back silicon substrate is an absolute pressure type, and thinning the back substrate if the back silicon substrate is a differential pressure type until the back cavity 11 can be communicated with the outside.
Wherein, the process of etching the back cavity 11 in the step a) adopts a wet etching process.
Wherein, the bonding process in the step b) is a fusion bonding process.
In the step d), an ohmic contact region and a piezoresistive strip 4 are prepared on the monocrystalline silicon piece pressure sensitive film by utilizing a thick boron doping process and a thin boron doping process, the thick boron doping process is omitted according to the process conditions, and the area of the piezoresistive strip 4 is directly connected with the metal lead 3.
Wherein, the MEMS film deposition process in the step d) is one of a thermal oxidation process, a low-pressure chemical vapor deposition process and a plasma enhanced chemical vapor deposition process.
Wherein, the MEMS metal film deposition process in the step e) is one of a sputtering deposition process, an electron beam evaporation deposition process and a heating evaporation deposition process.
Wherein, the etching process in the steps e), f) and h) is one of a dry ion etching process, a gas phase etching process, a wet anisotropic etching process and a wet isotropic etching process.
Having thus described the basic principles, essential features and advantages of the invention, it will be apparent to those skilled in the art that the invention is not limited by the foregoing embodiments, which are merely illustrative of the principles of the invention, but is susceptible to various changes and modifications without departing from the spirit and scope of the invention, as defined by the appended claims, and their equivalents.
Claims (8)
1. The utility model provides a two beam type minute-pressure sensing cores based on MEMS, includes pressure sensing core (1) and metal pad (2), interconnection lead wire (3), piezoresistive strip (4), sensitive film (8), passivation layer (9), insulating layer (10), back of the body chamber (11), support substrate support (12), its characterized in that: the pressure sensing chip body (1) is covered by a surface passivation layer (9) except a metal bonding pad (2) area for subsequent wire bonding, the metal bonding pad (2) and an interconnection lead (3) connect four piezoresistive strips (4) in an open-loop Wheatstone mode, the piezoresistive strips (4) comprise a transverse piezoresistive strip (4-1) and a longitudinal piezoresistive strip (4-2) and are arranged in a stress concentration area of a sensitive film (8), the sensitive film (8) is suspended above a back cavity (11) and supported by a supporting substrate (12), the piezoresistive strips (4) and the interconnection lead (3) are separated by an insulating layer (10) except contact positions, and a groove (7), a raised center block (5) and a double-beam structure (6) formed by etching are arranged on the sensitive film (8).
2. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 1, wherein: the method comprises the following steps:
a) etching a cavity with a V-shaped structure on the substrate wafer by using a wet etching bulk silicon process to serve as a back cavity (11) of the pressure sensing core body (1);
b) bonding a silicon wafer for preparing the sensitive film (8) on the silicon wafer forming the back cavity (11) by using a bonding process;
c) thinning the wafer of the sensitive film layer to a specified thickness by using a mechanical thinning process;
d) depositing a layer of silicon oxide on the surface of a bonded wafer by using a thermal oxidation process, preparing an ohmic contact region and a pressure resistance strip (4) on a pressure sensitive film of a monocrystalline silicon wafer by using a thick boron doping and light boron doping process, and repairing the lattice damage caused by injection by using an annealing process after the injection is finished;
e) corroding the silicon oxide layer on the sensitive film layer by using a corrosion process, and depositing on the monocrystalline silicon pressure sensitive film by using an MEMS film deposition process to form an insulating layer (10) with the thickness of 450 nm; and an etching process is utilized to form an end point electrical contact hole of the piezoresistive strip (4) on the insulating layer (10); depositing an Al metal film on the insulating layer (10) by using an MEMS film deposition process, forming a metal interconnection lead by patterning and then etching, and then ensuring the formation of an ohmic contact region between the piezoresistive strips (4) and the metal Al by using an annealing process;
f) after the patterning process, etching a corresponding groove with concentrated stress on the front surface of the sensitive film layer through an etching process;
g) depositing a surface passivation layer (9) on the upper layer of the patterned interconnection lead (3) by using an MEMS (micro-electromechanical systems) film deposition process, wherein the thickness of the surface passivation layer is about 500 nm;
h) and (3) opening electrode holes for routing with the outside at the PAD positions of four patterned metal leads (3) on the surface passivation layer (9) by utilizing an etching process, optionally, mechanically thinning the back silicon substrate, wherein thinning and non-thinning can be selected according to the application type of the prepared pressure sensing core body (1), thinning is not needed if the pressure sensing core body is an absolute pressure type, and the back substrate is thinned if the pressure sensing core body is a differential pressure type until the back cavity (11) can be communicated with the outside.
3. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: and the process of etching the back cavity (11) in the step a) adopts a wet etching process.
4. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: the bonding process in the step b) is a fusion bonding process.
5. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: in the step d), an ohmic contact region and a piezoresistive strip (4) are prepared on the monocrystalline silicon wafer pressure sensitive film by utilizing a thick boron doping process and a light boron doping process, the thick boron doping process is omitted according to the process conditions, and the area of the piezoresistive strip (4) is directly interconnected with the metal lead (3).
6. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: the MEMS film deposition process in the step d) is one of a thermal oxidation process, a low-pressure chemical vapor deposition process and a plasma enhanced chemical vapor deposition process.
7. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: the MEMS metal film deposition process in the step e) is one of a sputtering deposition process, an electron beam evaporation deposition process and a heating evaporation deposition process.
8. The process for preparing a MEMS-based dual beam type micro pressure sensing core according to claim 2, wherein: the etching process in the steps e), f) and h) is one of a dry ion etching process, a gas phase etching process, a wet anisotropic etching process and a wet isotropic etching process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111560497.9A CN114275731A (en) | 2021-12-20 | 2021-12-20 | MEMS-based double-beam type micro-pressure sensing core and preparation process thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111560497.9A CN114275731A (en) | 2021-12-20 | 2021-12-20 | MEMS-based double-beam type micro-pressure sensing core and preparation process thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114275731A true CN114275731A (en) | 2022-04-05 |
Family
ID=80873194
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111560497.9A Pending CN114275731A (en) | 2021-12-20 | 2021-12-20 | MEMS-based double-beam type micro-pressure sensing core and preparation process thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114275731A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115420952A (en) * | 2022-11-04 | 2022-12-02 | 之江实验室 | High temperature piezoresistive property measurement platform and method |
| CN115541071A (en) * | 2022-12-01 | 2022-12-30 | 无锡芯感智半导体有限公司 | Bipolar transistor type MEMS pressure sensor and preparation method thereof |
| US11965797B1 (en) | 2022-12-01 | 2024-04-23 | Wuxi Sencoch Semiconductor Co., Ltd. | Bipolar transistor type MEMS pressure sensor and preparation method thereof |
-
2021
- 2021-12-20 CN CN202111560497.9A patent/CN114275731A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115420952A (en) * | 2022-11-04 | 2022-12-02 | 之江实验室 | High temperature piezoresistive property measurement platform and method |
| CN115420952B (en) * | 2022-11-04 | 2023-03-24 | 之江实验室 | High temperature piezoresistive property measurement platform and method |
| CN115541071A (en) * | 2022-12-01 | 2022-12-30 | 无锡芯感智半导体有限公司 | Bipolar transistor type MEMS pressure sensor and preparation method thereof |
| US11965797B1 (en) | 2022-12-01 | 2024-04-23 | Wuxi Sencoch Semiconductor Co., Ltd. | Bipolar transistor type MEMS pressure sensor and preparation method thereof |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3114570B2 (en) | Capacitive pressure sensor | |
| JP3444639B2 (en) | Manufacturing method and apparatus for integrated pressure transducer | |
| EP1305586B1 (en) | Micro-machined absolute pressure sensor | |
| CN114275731A (en) | MEMS-based double-beam type micro-pressure sensing core and preparation process thereof | |
| CN111591952B (en) | MEMS piezoresistive pressure sensor and preparation method thereof | |
| CN104297520A (en) | Monolithic embedded integrated silicon acceleration and pressure composite sensor | |
| CN113371674A (en) | Wide-range pressure sensor chip and monolithic integration preparation method thereof | |
| CN105716750B (en) | A kind of MEMS piezoresistive pressure sensor and preparation method thereof | |
| US6860154B2 (en) | Pressure sensor and manufacturing method thereof | |
| CN112284607B (en) | Cross island high-temperature-resistant corrosion-resistant pressure sensor chip and preparation method thereof | |
| CN104864988A (en) | MEMS pressure sensor in silicon island-diaphragm structure, and manufacturing method thereof | |
| CN115127630B (en) | Preparation method of double-shaft multidirectional MEMS thermal flow sensor | |
| CN112034204A (en) | Linked contact capacitance type acceleration sensitive chip and manufacturing method thereof | |
| WO2020177339A1 (en) | Pressure sensor and manufacturing method therefor | |
| CN112284605B (en) | Cross island beam membrane high-temperature micro-pressure sensor chip and preparation method thereof | |
| CN111351607B (en) | Manufacturing method of temperature and pressure composite sensor | |
| CN111397776B (en) | Temperature and pressure composite sensor | |
| CN216559443U (en) | MEMS substrate and MEMS pressure sensor | |
| CN109813490B (en) | MEMS capacitive vacuum gauge and manufacturing method thereof | |
| CN111122904B (en) | Method for manufacturing sandwich accelerometer microstructure | |
| US6308575B1 (en) | Manufacturing method for the miniaturization of silicon bulk-machined pressure sensors | |
| JPH0554708B2 (en) | ||
| CN219823665U (en) | Pressure sensor chip | |
| CN214702570U (en) | Pressure sensor | |
| CN116553471A (en) | Pressure sensor chip and manufacturing method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |